The present invention relates to an air-cooled multi-cylinder internal combustion engine whose cylinders, arranged in a row (in-line) and clamped-in between the associated cylinder heads and the crankcase, are cast individually and are provided externally with transversely extending ribs for cooling purposes.
Such an internal combustion engine is disclosed in the DE-AS No. 12 05 772. The cooling air flowing transversely to the cylinders flows along the wide side of the cross ribs and is then deflected at the rear cooling air discharge side of the cylinders by columns shaped favorably from an aerodynamic point of view. Additionally, guide baffle or deflector plates are attached at the columns, however, nothing is stated in this prior art publication about how these plates are to be fastened. Customarily, such guide baffle or deflector plates are threadably secured and cause an undesired noise emission.
It is the object of the present invention to provide an air guide arrangement which can be manufactured and installed at low cost and does not represent an additional noise source.
A one-piece deflection member covering all cylinders at their cooling-air discharge side serves as solution to the underlying problems, which can be cast of light metal or even injection-molded of plastic material. For purposes of increasing its form rigidity, it is constructed double-walled. This deflection part is threadably connected either with the crankcase or with the cylinders. In the latter case, it can be used at the same time as knock bridge in that it further transmits the knock noises of all cylinders connected with the same to a knock sensor threadably secured thereon in the center thereof. If the deflection part is made of a material that has the same thermal coefficient of expansion as the crankcase, it follows the length expansions thereof during temperature changes so that the deflection part can be rigidly screwed onto the cylinders secured in the crankcase. Otherwise, also a compensating threaded connection can be selected which enables a differing length expansion of the deflection part and of the crankcase.